In modern telephony networks, service control points (SCPs) serve as an interface to telephony related databases, such as: call management service databases (CMSDB); line information databases (LIDB); and business services databases (BSDB). These databases are used, at least in part, to facilitate a variety of intelligent network (IN) type services including: find me service, follow me service, computer security service, call pickup service, store locator service, call waiting service, call block service, calling name delivery service, three way calling service, 800 number services, etc. Such telephony service databases may also be employed to provide communication service subscribers the flexibility to easily port their service from one communication service provider to another (i.e., number portability or local number portability).
It will be appreciated that the application of such SCP-type database services is not limited to the traditional wired public switched telephone network (PSTN), but is also widely implemented in the wireless telecommunications industry. Typical wireless network communication database applications include: home location registers (HLRs), visitor location registers (VLRs), authentication centers (AuCs), short message service centers (SMSCs), and equipment identification registers (EIRs). The term SCP is commonly used to broadly refer to a network element that includes a database system for providing database-intensive services, such as those discussed above.
It will also be appreciated that with the continuing convergence of traditional telecommunication networks and traditional data networks, the number and variety of converged or inter-network service related data-base applications designed to service the needs of combined data-telecommunications subscribers (e.g., presence service databases, telephony-to-WWW domain name servers, etc.) will increase dramatically in the future. As this converged network environment continues to evolve, so will the tendency of network operators to place SCP-like database nodes within the data network component of the converged network environment. That is to say, PSTN and wireless telephone network operators will likely find the economics of data network operation favorable to the placement of SCP-like database nodes within the data sub-network of the converged network environment, as opposed to the traditional PSTN—signaling system 7 (SS7) sub-network. As such, SCP and SCP-like network elements that have traditionally resided within an SS7 signaling network and been assigned a unique SS7 network address (point code and subsystem) would instead be placed within a data network, such as a transmission control protocol/Internet protocol (TCP/IP) based network, and would consequently be assigned an Internet protocol (IP) network address, hostname, and port number.
It will also be appreciated that in addition to database nodes, the convergence of telephony and data networks has led to the advent of numerous network elements that are associated with call setup and teardown functions which reside in or on the edge of the data network component of the converged communications network environment. Such network elements include media gateways (MGs), media gateway controllers (MGCs), and softswitch (SS) nodes, all of which are well known to those skilled in the art of Internet telephony. These nodes typically communicate using a data network based protocol (e.g., TCP/IP) in a manner similar to that of the SCP and SCP-like database nodes discussed above.
Shown in FIG. 1 is a sample converged communication network, generally indicated by the numeral 100. Converged network 100 includes a signaling system 7 (SS7) network component and an Internet protocol (IP) network component. The SS7 network component includes a service control point (SCP) 104, a signal transfer point (STP) 106, and an end office (EO) or service switching point (SSP) 108. It will be appreciated that these SS7 nodes are connected via dedicated SS7 communication links, and consequently communicate using SS7 formatted signaling messages. The IP network component includes an IP based database server (DBS) 112, a first media gateway controller (MGC) 114, and a second MGC 116. These IP nodes are connected via IP communication links, and consequently communicate using IP formatted signaling messages. A signaling gateway node (SG) 120 facilitates inter-network communication. SG 120 is adapted to communicate via one or more SS7 links with the SS7 network component, while simultaneously communicating with the IP network component via one or more TCP/IP connections or sockets. SG 120 provides a degree of signaling message protocol translation, such that signaling messages originating in the IP network may be properly communicated to the appropriate destination node in the SS7 network, and vice versa.
An example of this inter-network message communication functionality is also provided in FIG. 1. In this example, MGC node 116 formulates and transmits an IP-based query message, Q, that is ultimately destined for SCP node 104 in the SS7 network. However, it will be appreciated that the SS7 and IP sub-networks are separate and distinct entities that have a limited knowledge of each other's architecture or communication protocols. The query message passes through the IP network and eventually arrives at the signaling gateway node 120, where it is received, processed, and re-formatted into a form suitable for transmission through the SS7 network. A new SS7 query message, Q*, is subsequently generated and routed via STP 106 to the destination node, SCP 104. In response, SCP 104 generates an SS7 reply message, R*, which is routed via STP 106 back to SG 120. SG 120 again receives, processes, and re-formats the reply message into a form that is suitable for transmission through the IP network. The new IP reply message, R, is subsequently routed through the IP network back to MGC 116 in response to the original query.
The converged network architecture described above functions reasonably well; however, efficient and effective network management can become a significant problem in such networks. This difficulty arises from the same basic issue that was raised previously with regard to message routing; i.e., the SS7 and IP sub-networks are separate and distinct entities which have a limited knowledge of each other's architecture, communication protocols, and network management procedures.
With particular regard to the issue of network management, in a traditional SS7 signaling network there exist three categories of network management: traffic management, link management, and route management. Traffic management is the process of diverting messages away from failed links, while link management involves the activation and deactivation of signaling links. Route management is responsible for both re-routing messages around failed SS7 signaling points and controlling the flow of messages to any given signaling point in the network. Those skilled in the art of SS7 signaling network operation will appreciate such a network management strategy provides a layered approach to managing anomalistic events in an SS7 network. The SS7 protocol provides procedures designed to minimize the effects of network congestion and outages from the link level all the way up to the route level. Within the SS7 message transfer part (MTP) protocol, level two facilitates the detection of errors on individual signaling links. Level two is not concerned with communication abnormalities that arise outside the signaling point, but instead is adapted to resolve those issues associated with an individual signaling link. Again, it will be appreciated that every SS7 signaling link incorporates this function, which is controlled by level-three link management.
When an error is encountered, level two reports the error to level three, which in turn must then determine which error resolution procedures to invoke. In general, SS7 error resolution procedures begin at the lowest level, the link level, and work their way up to the highest level, the route level. While these procedures do not have a direct impact on routing or the status of signaling points, they do, however, trigger other level-three network management events.
Traffic management is effected by link management, primarily because traffic management must divert traffic away from a link that link management has failed and removed from service. For example, each SS7 signaling link may have a link buffer that stores messages to be transmitted. Once an acknowledgement is received from the receiving node, the corresponding message can be over-written or removed from the link buffer. If a message is not acknowledged within a predetermined time period, it will be retransmitted. Thus, messages must be stored in the link buffer until they are acknowledged.
When a signaling link fails, its associated link buffer in the transmitting node may contain many unacknowledged messages because the original messages may not have reached the destination or the acknowledgements may not have reached the source. Traffic management diverts traffic from the failed link to a new link and copies any unacknowledged messages from the link buffer associated with the failed link to the link buffer for the new link. The unacknowledged messages transferred to the new link buffer may then be retransmitted. In this manner, traffic management ensures the orderly delivery of all diverted traffic.
It should be noted that the traffic management process does not divert traffic away from a signaling point. The purpose of traffic management is simply to redirect traffic at a signaling point to a different signaling link associated with the signaling point. It is true, however, that the traffic management process does impact routes and route-sets to specific destinations. If a particular route is used by another signaling point to reach a destination, and traffic management has diverted traffic away from that route, adjacent signaling points may have to invoke route management procedures.
At the highest level, route management, unlike traffic management, diverts traffic away from signaling points that have become unavailable or congested. Regardless of the root cause, traffic management and link management will be involved at the affected signaling point. At the same time, all the signaling points around the affected signaling point are forced to invoke route management procedures to prevent messages from becoming lost.
In an SS7 network the above-described network management functionality is accomplished, in part, through the use of specific network management messages. A sample structure of a typical SS7 network management message or message signaling unit (MSU) 150 is illustrated in FIG. 2. It will be appreciated by those skilled in the art of SS7 signaling communications that signaling information field (SIF) 152 of MSU 150 contains data associated with a particular point code that is experiencing difficulty or a particular link that has failed. Additional status information, priority codes, and other relevant maintenance codes may also be included in SIF parameter 152, depending upon the particular type of network management message being sent.
There are a number of routing management messages that are commonly employed to re-direct traffic around a failed or congested route. Again, it will be appreciated that such messages may be sent by an SS7 signaling point in response to the failure of one or more provisioned links. More particularly, when a route fails, a routing management message is sent to all neighboring SS7 signaling nodes (i.e., those SS7 signaling nodes that are adjacent to the troubled signaling node). This routing management message informs the neighboring SS7 signaling nodes of the problem at the troubled node and also provides instructions regarding future routing to the troubled node. It will also be appreciated that routing management messages are also used to inform neighboring SS7 signaling nodes of the recovery of a previously troubled node. Such SS7 routing management messages include: transfer prohibited (TFP), transfer restricted (TFR), transfer controlled (TFC), transfer allowed (TFA) messages, transfer cluster prohibited (TCP), and transfer cluster allowed (TCA). These messages are only a subset of all network management messages defined in the SS7 protocol. A comprehensive discussion of SS7 network management and related issues can be found in Signaling System #7 by Travis Russell, McGraw-Hill Publishing 1998.
A transfer prohibited (TFP) message is generated and transmitted by an SS7 signaling point (e.g., an STP) in response to determining that communication with an SS7 node is no longer possible. In response to determining that communication with an SS7 node is possible, but sub-optimal, a transfer restricted (TFR) message is sent. A TFR message essentially requests that adjacent SS7 signaling points use alternate routes when sending messages to the troubled SS7 node. If alternate routes are not available, messages may continue to be routed normally. A transfer controlled (TFC) message is sent by an SS7 signaling point (e.g., STP) in response to the receipt of an MSU that is destined for a congested route. In such a scenario, the MSU is discarded and a TFC message is returned to the originator or sender of the MSU. A transfer allowed (TFA) message is sent by an SS7 signaling point when a previously failed route once again becomes available.
Shown in FIG. 3 is a scenario involving network management message flow in converged communications network 100 described above with regard to FIG. 1. In this example, it is assumed that the SS7 communication link that connects STP 106 and SCP 104 has failed. In response to the detection of this failure, STP 106 transmits a transfer prohibited (TFP) network management message to each of it's neighboring SS7 signaling points, SSP 108 and SG 120. Consequently, both SSP 108 and SG 120 are made aware that they should not attempt to send any SS7 MSU traffic to SCP 104 via a route that involves STP 106.
It will be appreciated that, in the absence of such proactive network management procedures, SSP 108 and SG 120 might flood STP 106 with MSUs as a result of continuous, repeated attempts to obtain a response from the failed or inaccessible SCP 104. In such a scenario, STP 106 could incur significant congestion that might interfere with or prevent the routing of messages to other available SS7 signaling nodes in the network. As such, it is possible that the failure of one node in the network could potentially lead to the failure of another, and so on. It is precisely this situation that SS7 network management procedures are designed to prevent.
Given the discussion above, a significant problem encountered with converged networks now becomes more apparent. As shown in FIG. 3, SSP 108 and SG 120 are notified that they should no longer send messages to SCP 104. However, since nodes in the IP component of the converged network are not capable of directly receiving and interpreting SS7 messages, there is no method of notifying any IP nodes in the IP sub-network that messages destined for SCP 104 should not be sent. Those skilled in the art of IP network operation will appreciate that some transport and higher layer protocols in the IP protocol stack employ periodic retransmission of messages if no response or acknowledgment is received within a pre-defined acknowledgment interval. As such, SG 120 may become flooded with re-transmitted query messages, destined for SCP 104, from nodes within the IP network. Again, it will be appreciated by those skilled in the art of communication network operations that such a scenario can have significant adverse impacts on the overall viability of the converged network.
Therefore, what is needed is a system and method of extending network management functionality in converged communication network environment such that anomalistic events, and any subsequent resolution procedures, occurring in one sub-network component of the converged network can be effectively communicated to another sub-network component of the converged network. cl DISCLOSURE OF THE INVENTION
The present invention includes a communications network element that is capable of routing messages and also performing inter-network management functions in a converged telephony-data network environment. In one embodiment, the present invention is implemented in the form of a signaling gateway routing node which is adapted to facilitate signaling communication between nodes in a signaling system 7 network and nodes in an Internet protocol (IP) network. In addition to basic message routing functionality, the signaling gateway routing node is adapted to notify nodes in the IP network when a node in the SS7 network becomes congested or unavailable. In certain cases, the signaling gateway selectively notifies only IP nodes that are concerned with the status of the troubled SS7 node; while in other cases, notification messages are broadcast to all relevant IP nodes. The signaling gateway also serves to limit the number of status queries or polling messages that are conveyed from IP nodes through to the distressed SS7 node, thereby reducing needless congestion in the SS7 network during a node distress episode. By doing so, the signaling gateway routing node according to an embodiment of the present invention provides much needed network management service in the converged telephony—data network environment.
The functions for providing converged network management are described herein as modules or processes. It is understood that these modules or processes may be implemented as computer-executable instructions embodied in a computer-readable medium. Alternatively, the modules or processes described herein may be implemented entirely in hardware. In yet another alternative embodiment, the modules or processes described herein may be implemented as a combination of hardware and software.
The processes and modules for providing converged network management functionality are described below as being associated with cards or subsystems within a gateway routing node. It is understood that these cards or subsystems include hardware for storing and executing the processes and modules. For example, each card or subsystems described below may include one or more microprocessors, such as an ×86 microprocessor available from Intel Corporation, and associated memory.
Accordingly, it is an object of the present invention to provide a routing node that facilitates the inter-network communication of network management type messages in a converged network environment.
It is another object of the present invention to provide a system and method for use in a converged network environment whereby an Internet protocol (IP) device is able to divert traffic from one of a mated pair of signaling gateway (SG) nodes to the other in the event that one of the mated SG nodes is not able to access a particular destination point code.
It is yet another object of the present invention to provide a system and method for use in a converged network environment whereby an IP device is able to audit the status of a point code associated with an SS7 signaling point.
It is yet another object of the present invention to provide a system and method for use in a converged network environment whereby network management information associated with a distressed SS7 node is distributed to concerned nodes in an IP network.
It is yet another object of the present invention to provide a system and method for use in a converged network environment whereby an IP device may be notified of congestion in an SS7 sub-network component of the converged network environment.
It is yet another object of the present invention to provide a system and method for use in a converged network environment whereby an IP device is able to assist in the abatement of congestion in an SS7 sub-network component of the converged network environment.
It is yet another object of the present invention to provide a system and method for use in a converged network environment whereby an IP device is able to obtain SS7 User Part Unavailability status from in an SS7 sub-network component of the converged network environment.
It is yet another object of the present invention to provide a system and method for use in a converged network environment whereby only one of a plurality of similar status request queries or polling messages sent by IP nodes is permitted to enter an SS7 network component of the converged network.
It is yet another object of the present invention to provide a system and method for use in a converged network environment whereby the receipt of a single SS7 network management message results in the distribution of multiple IP messages containing the SS7 network management message information.
Some of the objects of the invention having been stated hereinabove, other objects will become evident as the description proceeds, when taken in connection with the accompanying drawings as best described hereinbelow.